1. Field of the Invention
The present invention relates to a fuse used in a circuit controlling power supply to a load through a relay circuit.
2. Description of the Related Art
An electrical junction box mounted in an automobile or an in-vehicle electric control unit has a function of distributing battery power to a predetermined load. As shown in FIG. 1, an electrical junction box 100 of a related art includes a fuse 102, a semiconductor relay 103 and a relay control circuit (unillustrated). The fuse 102 receives an input of an electric current from the battery 101, and prevents the electric current from being excessively supplied from the battery 101. The semiconductor relay 103 either allows or does not allow the electric current supplied through the fuse 102 to flow into a load 110. The relay control circuit controls the semiconductor relay 103. The semiconductor relay 103 is mounted on a board 104 housed in a package 100a. The relay control circuit is formed of an electronic component (unillustrated) mounted on the board 104 and of a circuit pattern (unillustrated) formed on the board 104. Japanese Patent Application Publication No. 2002-359349 discloses an example in which the semiconductor relay 103 is mounted on the board 104 in the package 100a. 
In another related example, as shown in FIG. 2, a mechanical relay is used instead of the semiconductor relay 103 while being mounted on a board 104 as similar to the semiconductor relay 103. Here, the description of this related example will be provided by giving the same reference numerals as shown in FIG. 2 to the same components as described in the foregoing related example while excluding the redundant explanations of the same components.
A fuse 102 is a plug-in type fuse attached to a tuning fork terminal (unillustrated) provided to a package 100a of an electrical junction box 100. As shown in FIG. 3, the fuse 102 includes a first connecting terminal 102a, a second connecting terminal 102b arranged in parallel with the first connecting terminal 102a, and a fuse element 102c provided between these two terminals 102a and 102b. The fuse 102 has an integral structure formed by sealing, with a mold resin sealing portion 102d, the fuse element 102c and the first and second connecting terminals 102a and 102b excluding portions to be connected to corresponding terminals. The tuning fork terminal to which the fuse 102 is attached is provided outside the package 100a from the viewpoint of convenience in maintenance, check and the like.
In the related example, however, the semiconductor relay 103 and the mechanical relay 105, which are heat sources, are mounted on the board 104 inside the package 100a. Accordingly, spaces for installing the semiconductor relay 103 and the mechanical relay 105 need to be secured on the board 104 and the like. This is one of the factors of increasing the size of the board 104 and accordingly the size of the package 100a including the board 104 therein. Since the relay circuits are heat sources, the board 104 and the like need to be made of a high-heat-radiation material and a high-heat-resistant material. Use of such materials requires high costs for manufacturing the board 104. In addition, when the semiconductor relay 103 or the mechanical relay 105 breaks down, the board 104, as a whole, has to be exchanged. Hence, this configuration has poor maintainability.